Related Experiment Video
Updated: Apr 14, 2026

Protocol for the Synthesis of Ortho-trifluoromethoxylated Aniline Derivatives
Published on: January 19, 2016
Acetyl Methyl Torsion in N-Ethylacetamide: A Challenge for Microwave Spectroscopy and Quantum Chemistry
Raphaela Kannengießer1, Marcel J Lach1, Wolfgang Stahl1
1Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074 Aachen (Germany).
Abstract:
The gas-phase structures and parameters describing acetyl methyl torsion of N-ethylacetamide are determined with high accuracy, using a combination of molecular beam Fourier-transform microwave spectroscopy and quantum chemical calculations. Conformational studies at the MP2 level of theory yield four minima on the energy surface. The most energetically favorable conformer, which possesses C1 symmetry, is assigned. Due to the torsional barrier of 73.4782(1) cm(-1) of the acetyl methyl group, fine splitting up to 4.9 GHz is found in the spectrum. The conformational structure is not only confirmed by the rotational constants, but also by the orientation of the internal rotor. The (14) N quadrupole hyperfine splittings are analyzed and the deduced coupling constants are compared with the calculated values.
Related Concept Videos
Structures of Carboxylic Acid Derivatives
Carboxylic acid derivatives contain an acyl group attached to a heteroatom such as chlorine, oxygen, or nitrogen. The carbonyl carbon and oxygen are both sp2-hybridized with an unhybridized p orbital.
The three sp2 orbitals of the carbonyl carbon form three σ bonds, one each with the carbonyl oxygen, the α carbon, and the heteroatom, whereas the other two sp2 orbitals of the carbonyl oxygen are occupied by the lone pairs. Further, the...
Amines to Amides: Acylation of Amines
Next, the second equivalent of amine serves as a Brønsted base and deprotonates the quaternary...
Alkylation of β-Ketoester Enolates: Acetoacetic Ester Synthesis
Preparation of Alkynes: Alkylation Reaction
Alkylation of terminal alkynes with primary alkyl halides in the presence of a strong base like sodium amide is one of the common methods for the synthesis of longer carbon-chain alkynes. For example, treatment of 1-propyne with sodium amide followed by reaction with ethyl bromide yields 2-pentyne.
Phase II Reactions: Acetylation Reactions
The substrates for acetylation are typically drugs or their metabolites with an amino, sulfonamide, or hydrazine functional group. Acetylation can occur at several points in the drug molecule, including primary, secondary, and...
¹H NMR of Conformationally Flexible Molecules: Temporal Resolution

